A multiple-input multiple-output (MIMO) antenna technology is a core technology among new generation wireless communications technologies. When a transmit node uses multiple antennas to send a resource, two schemes can be used: diversity and multiplexing.
A diversity scheme means that when using M antennas to send a resource, a transmit node provides a diversity based on the M antennas for the resource that needs to be sent, and sends different copies of the resource by using the M antennas, and a receive node combines the different copies of the resource that are received from the M antennas in the diversity into the required resource. When the diversity scheme is used, a high signal to interference plus noise ratio (SINR) may be generated at a receive end, thereby increasing a coverage distance, or increasing a transmission rate at a same coverage distance. In addition, in the diversity scheme, a receive node does not need to provide a measurement feedback on channel state information (CSI), thereby improving link robustness. Therefore, in a wireless communications system that uses a MIMO technology, a transmit diversity scheme is used as a mandatory multi-antenna transmission scheme.
In a current wireless communications system, only a one-dimensional antenna transmit diversity is achieved based on two or four antennas; however, for a wireless communications system that uses a two-dimensional array antenna, no multi-antenna transmit diversity scheme is available.